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Older people slower but smarter than young'uns

Retirees might take longer to fill out a crossword than their kids, but they'll leave fewer blanks. Viviane Richter reports on a study that shows different types of intelligence peak during different decades.

Human intelligence is wired to peak at different stages of life – and it turns out the brain saves some goodies for the golden years, American scientists found.

The ability to think quickly and recall information, known as “fluid intelligence”, was long thought to reach its pinnacle at around 20 years old, followed by a slow, unrelenting decline.

But the picture’s more complicated than that.

A pair of researchers from the Massachusetts Institute of Technology and Massachusetts General Hospital collected online IQ and memory tests from more than 48,000 participants, which measured around 30 aspects of intelligence, including digit memorisation, visual search and assembling puzzles.

“We were mapping when these cognitive abilities were peaking, and we saw there was no single peak for all abilities. The peaks were all over the place,” study co-author Joshua Hartshorne described.

Where raw speed in processing information peaked around the age of graduating high school, short-term memory improved until age 25 and didn’t decline until age 35.

But the ability to evaluate other people’s emotional states didn’t peak until the 40s and 50s, the data showed. And the most stellar performers in vocabulary intelligence were participants in their late 60s or early 70s.

“At any given age, you’re getting better at some things, you’re getting worse at some other things, and you’re at a plateau at some other things,” Hartshorne explained.

“There’s probably not one age at which you’re peak on most things, much less all of them.”

The authors attribute these late intelligent blooms to today’s better education, more jobs that require reading and better intellectual stimulation for older people.

How the brain rewires intelligence at a molecular level remains unclear, but previous studies indicated changes in gene expression and brain structure could play a role, the authors point out.

“You see these lifespan patterns that we don’t know what to make of,” said study co-author Laura Germine. “The brain seems to continue to change in dynamic ways through early adulthood and middle age.”

The researchers are continuing their studies using the online quizzes, now with added brain-probing tasks designed to test social and emotional intelligence, language skills and executive function.

“We took the existing theories that were out there and showed that they’re all wrong. The question now is: What is the right one? To get to that answer, we’re going to need to run a lot more studies and collect a lot more data,” Hartshorne said.